Pinus koraiensis is recognized as one of the most valuable timber and economic tree species. Fruiting properties and growth traits are important characteristics for P. koraiensis breeding, and the relationship between fruiting properties of parents and growth traits of progeny is needed for better understanding. In this study, 71 parental clones and open-pollinated progeny families from the same plus trees were used as materials, and four fruiting properties (cone number per single tree, seed number per single cone, thousand-seed weight, and fruiting individual percentage) and four growth traits (height, diameter at breast height, volume, and survival individual percentage) were measured and calculated. There were significant variations in fruiting properties and growth traits among parental clones and progeny families. For fruiting properties, the phenotypic and genotypic coefficients of variation ranged from 16.51% to 175.34% and from 6.75% to 20.26%, respectively, and the repeatability ranged from 0.3430 to 0.9438. For growth traits, the phenotypic and genotypic coefficients of variation ranged from 15.68% to 39.89% and from 3.51% to 25.99%, respectively, and the broad-sense and narrow-sense heritability ranged from 0.7149 to 0.9681 and from 0.3648 to 0.4614, respectively. There were extremely significant positive correlations between cone number per single tree and fruiting individual percentage, as well as between height, diameter at breast height, and volume. Nevertheless, there was no significant correlation between fruiting properties of parental clones and growth traits of progeny families. Based on the integrated results of principal component analysis and the multi-trait comprehensive evaluation method, six clones (HS23, HS95, HS05, HS73, HS67, and HS17) and four families (HS37, HS17, HS60, and HS54) were selected as elite clones and families, respectively, and HS17 was identified as both an elite parental clone and an elite progeny family. The genetic and realistic gains of elite clones for fruiting properties ranged from 1.34% to 17.34% and from 1.50% to 47.22%, respectively, and the genetic and realistic gains of elite families for growth traits ranged from 4.85% to 33.90% and from 6.73% to 35.02%, respectively. The present study provides the foundation for reconstruction and upgrading of P. koraiensis seed orchards, which is helpful for increasing productivity and economic benefits.

Establishing mixed conifer–broadleaf forests enhances soil multi-nutrient cycling (SMC), yet the underlying mechanisms, particularly the role of rhizosphere microbial communities, remain poorly understood. This study investigated how bacterial and fungal communities in the rhizosphere soil of Larix olgensis drive SMC in both pure and mixed plantations with Fraxinus mandshurica, elucidating the microbial pathways for nutrient supply in mixed stands. Our results indicated that SMC in the L. olgensis rhizosphere soil was significantly greater in mixed stands (0.43) than in pure stands (−0.51). Tree species mixing significantly enhanced microbial diversity, increased the stochasticity of community assembly, and reduced dispersal limitation. Cross-kingdom (bacteria–fungi) co-occurrence networks in mixed stands showed a 19.7% increase in positive correlations, indicating stronger microbial cooperation. Random forest analysis identified microbial diversity, network complexity, and bacterial assembly processes as the main predictors of SMC. Structural equation modeling indicated that microbial diversity indirectly promoted SMC via increased network complexity, while bacterial assembly processes directly influenced SMC. These findings demonstrate that mixed conifer–broadleaf plantations improve soil microbial functioning and nutrient cycling by modifying microbial diversity, assembly processes, and interaction networks.

Biodiversity maintenance mechanisms have been central to the study of community ecology, and the negative density dependence effect plays an important role in maintaining species diversity in forest communities. However, the strength and direction of the negative density dependence effect may change at different latitudinal gradients, and theory predicts that the negative density dependence effect increases with decreasing latitude. Using three provinces in northeastern China as the study target, we selected forest ecosystems in 15 locations according to the latitude gradient and analyzed the mixing of large- and small-diameter trees and adjacent tree species at different latitudinal gradients by the second-order characteristic function of mark mingling (The species mingling was used as “constructed marks” and we developed a second-order characteristic function of mark mingling useful for comparing spatial species mingling via random assignment of species patterns at specific ecological scales). It was found that the tree species mixed level of the large trees was higher, that of the small trees was lower in the stands at the middle and low latitudes (40, 41, and 43), and the tree species mixed level of the large or small trees was lower in the stands at high latitudes (45 and 46). Also, the level of mixing of large trees with surrounding tree species was significantly different among latitudes within the small scale (0–5 m). More importantly, the peak value of the difference in the second-order characteristic function of mark mingling (Δv(r)) of the stand increased gradually with decreasing latitude. The results indicated that the difference in tree species mixing degree between large and small trees was increasing, and this phenomenon was more obvious at the small scale (0–10 m). In general, we found that the negative density dependence effect in the late successional forest system showed a variation trend with latitude gradient, which showed that with the decrease in latitude, the negative density dependence effect in the stands was increasing. The results showed that in temperate forests, in low-latitude stands (40–43° N), there is significant peak in species mingling differences at small scales (0–10 m). Spatial heterogeneity thinning should be prioritized, and rare tree species should be replanted within a 10 m radius to alleviate intraspecific competition. In contrast, in high-latitude stands (45–46° N), human disturbance should be reduced to maintain the natural community structure. These measures can provide precise management strategies for regional biodiversity conservation. This study revealed the response of the intensity of the negative density dependence effect to changes in latitudinal gradients, and provides new ideas for maintaining and controlling regional species diversity.

Soil nematodes are integral to soil micro-food webs and serve as sensitive bioindicators of soil ecological condition. However, how forest vegetation and soil properties interact to shape nematode community assembly, network structure, and functional stability remains inadequately understood. Using 18S rRNA gene amplicon sequencing coupled with phylogenetic null modeling, we examined soil nematode communities across four forest types along a succession gradient. Although taxonomic diversity (e.g., Shannon and Pielou indices) differed significantly among forest types, network topology and stochastic assembly processes were more closely associated with community restructuring and co-occurrence patterns. This suggests that, while diversity is not irrelevant, network- and assembly-based metrics provide complementary and often more sensitive indicators of nematode community responses to forest type. Co-occurrence network analysis revealed that mixed forests fostered more complex and potentially stable networks, whereas plantations formed dense but potentially vulnerable networks. Assembly processes were not dominated by strong deterministic selection (|βNTI| ≤ 2 for most comparisons), a pattern consistent with undominated processes (e.g., ecological drift, weak environmental filtering). Dispersal limitation played a negligible role in this system. Partial Least Square Path Modeling identified spatial factors and key soil properties (e.g., pH, electrical conductivity, soil water content, and organic carbon) as primary drivers of community structure. Our findings indicate that assessing soil food web health should integrate network analysis and stochasticity metrics rather than rely solely on taxonomic diversity. For sustainable forest management, mixed-species stands are preferable to monoculture plantations, and maintaining soil physicochemical heterogeneity is critical for community stability.